Tube making machine with diameter control and method

ABSTRACT

A spiral pipe forming system which includes automatic diameter or dimension sensing and control.

This application claims the benefit of U.S. Provisional Application No. 61/011677, titled “Tube Making Machine with Diameter Control and Method,” filed Jan. 18, 2008, inventor William J. Kephart, which application is hereby incorporated by reference.

I. BACKGROUND OF THE INVENTION

A. Field of the Invention

The present invention relates to machines and methods for making spiral pipe from strips of sheet metal and, in particular, to machines and methods for accurately monitoring and controlling the diameter of such pipe. As used here, “pipe,” tube” and “conduit” are used interchangeably.

B. Description of the Related Art

Commonly assigned U.S. Pat. No. 3,940,962 describes a three-roll conduit forming mill and diameter control of Pacific Roller Die Company, Inc. The '962 patent is incorporated by reference in its entirety. As described in the '962 patent, the adjacent spiral edges of a strip which forms a spiral conduit are joined by interlocked edge flanges which are pinched or crimped tightly together by upper and lower lock-up rolls. The radial positioning of this pair of rolls relative to the conduit axis controls the diameter of the conduit. Thus, when the rolls are simultaneously raised, i.e., moved radially inward relative to the axis of the conduit, the diameter of the conduit increases When the rolls are simultaneously lowered, i.e., moved radially outward relative to the conduit axis, the diameter of the conduit decreases. The position of the lock-up rolls is changed by control screws which are manually turned using wrenches. The '962 patent indicates the diameter changes effected by such movement are minor and occur gradually. For instance, in a machine for making 1 to 36 inch conduit, such adjustments may be used to effect diameter changes of approximately ±¼ (one-fourth) inch.

The '962 patent also discloses the feasibility of making the adjustment automatic, by including means for monitoring the diameter, such as a belt or loop detector, which, when it senses a given diameter deviation would activate a servomechanism which in turn lowered or raised the lock rolls to correct the deviation.

II. SUMMARY OF THE INVENTION

In one aspect, the present invention is embodied in a mill for forming a spiral pipe, comprising: apparatus for forming a spirally wound sheet, the apparatus including inner and outer pressure rolls engaging and crimping together adjacent edges of the spirally wound sheet; a sensing system for monitoring changes in the diameter of the spirally wound sheet as it is formed and responsively generating signals including information regarding changes in diameter; and a system responsive to the output signals for moving the inner and outer pressure rolls in unison radially inward or outward relative to the axis of the pipe to offset change in diameter.

In another aspect, the present invention is embodied in a method of forming a spiral pipe with diameter control, comprising: forming a spirally wound sheet having adjacent edges; crimping adjacent edges of the sheet together; monitoring the diameter of the spirally wound sheet for changes therein; responsive to change in the diameter, generating signals including information regarding changes in diameter; and responsive to the signals, moving the adjacent edges of the spirally wound sheet together radially inward or outward relative to the axis of the spirally wound sheet to offset the change in diameter.

III. BRIEF DESCRIPTION OF THE DRAWING

FIG. 1 is a perspective view of a three roll pipe-forming mill.

FIG. 2 is an enlarged partial view of the mill of FIG. 1, depicting an automatic diameter sensing system.

FIG. 3 is a schematic of an automatic diameter sensing and control system.

IV. DETAILED DESCRIPTION OF THE PREFERRED EMBODIMENT(S)

FIG. 1 depicts a three-roll pipe forming mill 10 by Pacific Roller Die Company, Inc. The system includes a roll former system 12 for feeding a metal strip 1 to a three roll system 14, which forms the strip into a helical pipe 3. Diameter sensing and control system 16, FIGS. 2 and 3, monitor the diameter of the formed pipe 3 and responsively controls the diameter of the pipe as it is formed, as indicated by reference numeral 2.

As is well known and as described more fully in U.S. Pat. No. 3,940,962, the roll former 12 comprises a carriage 22 which is supported by casters 24 so that the oblique angle formed between the roll former and the three roll system can be varied. The carriage 22 is an elongated frame which mounts a plurality of corrugating rolls 10, arranged in a plurality of stands of matched pairs of upper and lower rolls. The rolls are horizontally aligned so that a strip 1 which is input to the roll former 12 passes through the upper and lower rolls of each stand and is deformed thereby into a corrugated profile, then exits the roll former and enters the three roll system 14.

The operation of the three roll system 14 is also well known and thus is described in conjunction with the construction and operation of the diameter (or dimension) sensing and control unit 16 and the diameter or dimension sensor or monitor 15 of system 16. Referring to FIG. 2, the diameter sensing mechanism 15 includes a support 26 comprising a horizontal base member 28, legs 30 and 32 and a horizontal top member 34. The legs 30 and 32 are bolted to the floor or other stationary base. A pivot arm 36 is pivotally mounted at one of a plurality of mounting holes 38 spaced along the lengthwise dimension of leg 30. A tension spring 42 is pivotally mounted at one end to the pivot arm 36 and is pivotally mounted at the other end to bottom leg 28. A wire (or rope or cable, etc.) 40 is mounted at one end to winch 44, is wrapped one full loop around formed pipe 3, and is attached at the opposite end to the pivot arm 36. Winch 44 and tension spring 42 bias or pull the pivot arm 36 in opposite directions, such that the winch can be used to orient the pivot arm in a desired orientation and the tension spring tends to maintain the pivot arm in the selected orientation. A sensor 46 such as an ultrasonic sensor is mounted on top member 34 and is focused or directed onto the pivot arm 36 and provides an output signal containing information regarding the distance between the sensor and the pivot arm. During operation of the three roll system 14, changes in the diameter of the pipe 3 effect movement of the cable 40 and the pivot arm 36, causing variations in the output signal which are representative of the changes in the diameter, radius, perimeter or other dimension which is being monitored.

The diameter or dimension control system 16 for the pipe forming mill 10 is depicted in FIG. 2 and, in particular, in FIG. 3. The three-roll forming arrangement 14 of Pacific Roller Die Company includes lead rolls 52, which engage the lower surface of sheet 1 entering the three roll system 14, mandrel rolls 56 and interior pressure roll 54 on the upper side of the sheet, i.e., the interior of the forming pipe 2, and buttress rolls 58 which shape the sheet helically into the pipe 2. Exterior pressure roll 62 engages the exterior surface of the pipe 2 opposite the interior pressure roll 54 and the two rolls cooperatively crimp the mating adjacent edges of the spirally formed sheet and thereby join the pipe along the adjacent sheet edges. The internal pressure roll 54 and the external pressure roll 62 are mounted to positioning devices which cooperatively move the internal pressure roll and the external pressure roll radially inward and outward together relative to the axis of the pipe for effecting the crimping action. The positioning device for the internal pressure roll 54 comprises a wedge 64 and mandrel 66 arrangement and a hydraulic cylinder 68. The internal pressure roll 54 is connected to the mandrel 66 which in turn is mounted to piston/shaft 72 of the hydraulic cylinder 68. When the hydraulic cylinder 68 is operated to move the shaft thereof bidirectionally, in opposite directions shown by arrow 74, the mandrel 66 cams the wedge 64 along mandrel and moves the internal pressure roll 54 radially outward (down) or radially inward (up).

The external pressure roll 62 is mounted to shaft or piston 76 of hydraulic jack 78. Bidirectional movement of the jack piston 76, as indicated by arrow 82, moves the external pressure roll 62 radially inward (up) or outward (down). Synchronized inward or outward movement of the external pressure roll 62 and the internal pressure roll 54 shifts the position of the crimped edges of the pipe inward and outward relative to the pipe axis.

Referring further to FIG. 3, the output side of sensor 46 is connected to control box 84, which can be a separate device or part of the programmable logic device or computer which controls the system 10. The control box is connected to a directional control valve and check valve arrangement 86 and to an air operated hydraulic pump unit 88. The directional control valve and check valve 86 is connected to the hydraulic cylinder 68 for providing electronic control of the hydraulic fluid which operates the hydraulic cylinder so that the piston thereof is translated bidirectionally, as discussed above, for camming the wedge 64 along mandrel 66 and moving the internal pressure roll 54 radially in and out. The air-operated hydraulic pump unit 88 is connected to the external pressure roll jack 78 for providing electronic signal controlled, air-operated hydraulic flow to that jack, for moving the piston 76 thereof bidirectionally, as discussed above, and thereby moving the external pressure roll 62 radially in and out.

When the size of the pipe 3 changes, downward or counterclockwise pivoting of the pivot arm 36 is associated with decreases in pipe size, whereas upward or clockwise pivoting of the pivot arm is associated with increases in pipe size. The output from ultrasonic sensor 46 causes control box 84 to operate the internal and external pressure roll positioning devices in unison, and simultaneously move the internal pressure roll 54 and the external pressure roll 62 inward or outward relative to the pipe axis and thereby respectively increase or decrease the diameter of the pipe.

The present invention has been described in terms of preferred and other embodiments. The invention, however, is not limited to the embodiments described and depicted. Adaptation to other embodiments will be readily done by those of usual skill in the art, limited only by the claims appended hereto. 

1. Apparatus for forming a spiral pipe, comprising: apparatus for forming a spirally wound sheet, the apparatus including inner and outer pressure rolls engaging and crimping together adjacent edges of the spirally wound sheet; a sensing system for monitoring changes in the diameter of the spirally wound sheet as it is formed and responsively generating signals including information regarding changes; and a system responsive to the output signals for moving the inner and outer pressure rolls in unison radially inward or outward relative to the axis of the pipe to offset change in diameter.
 2. A method of forming a spiral pipe having controlled diameter, comprising: forming a spirally wound sheet having adjacent edges; crimping adjacent edges of the sheet together; monitoring the diameter of the spirally wound sheet for changes therein; responsive to change in the diameter, generating signals including information regarding the change; and responsive to the signals, moving the adjacent edges of the spirally wound sheet together radially inward or outward relative to the axis of the spirally wound sheet to offset the change in diameter. 